BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012 segment	Sep. 30, 2011	Sep. 30, 2012 segment	Sep. 30, 2011
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Insurance Business Segments	2		2
Earned premiums	$ 5,660	$ 5,210	$ 16,505	$ 15,037
Net investment income	869	843	2,597	2,422
Other income	32	17	64	63
Realized investment gains (losses)	286	(83)	(177)	(1,330)
Total revenues	6,847	5,987	18,989	16,192
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums	4,405	4,018	12,769	11,490
Net investment income	713	695	2,134	1,980
Other income	22	7	38	33
Total business segment revenues	5,140	4,720	14,941	13,503
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums	1,254	1,192	3,736	3,547
Net investment income	153	147	457	439
Other income	5	3	10	8
Total business segment revenues	1,412	1,342	4,203	3,994
Other business segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total business segment revenues	10	13	40	40
Total Business Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total business segment revenues	6,562	6,075	19,184	17,537
Corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	65	62	197	183
Intercompany eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	$ (66)	$ (67)	$ (215)	$ (198)